Automatic throttle torque-responsive power tool

ABSTRACT

A fluid-operated power screwdriver having a torque-opening clutch and a throttle which is opened by the operator pressing the screwdriver against a fastener and closed in response to the opening of the clutch. The opening of the clutch moves a control sleeve to a locking position whereby the throttle is allowed to close.

United States Patent Inventors John M. Clppp;

John P. Kruug, both 01 Athens, Pa. Appl No, 820.940 Filed May 1,1969 Patented July 10, I971 A gnec lngersoll-iloqq Company New Yorls NX.

AUTOMATIC THROTTLE TORQUE'RESPONSIV E Primary ExaminerBenjamin W. Wychc Attorneys-Carl R. Horten and David W. Tibbott POWER TOOL l4claimssnnwlng ABSTRACT: A fluid-operated power screwdriver having 3 us. C1 192/150, torque-Opening Clumh and a throttle which is pened y he 1921.034, 192/56 R, 81/524 operator pressing the screwdriver against a fastener and Int. Cl HM 43/20 closed in response to the opening of the clutch The opening Field 0! Search H 192/.034, of the clutch moves a control sleeve to a locking position 150 whereby the throttle is allowed to close,

PATENTED JUL20 ISYI lNVENTORS JOHN M. CLAPP ATTORNEY BY M F /6'. 4

JOHN P. KROUSE AUTOMATIC THROTTLE TORQUE-RESPONSIVE POWER TOOL BACKGROUND OF THE INVENTION This invention relates to the art of power-operated rotary tools such as power screwdrivers and power wrenches.

It is conventional to provide a power-operated screwdriver or the like with a torque-controlled clutch which automatically disconnects the tool spindle from its motor when the torque load on the spindle rises to a predetermined value. In addition, it is conventional to provide a compressed airoperated screwdriver with a throttle which automatically opens to start the screwdriver motor when it is pressed against a screw and closes to stop the screwdriver when it is withdrawn from a screw.

SUMMARY OF THE INVENTION The principal object of this invention is to combine a torque-controlled clutch with a motor starting and stopping means in a novel manner whereby a tool using the combination will stop its motor and simultaneously disconnect the motor from the spindle or bit when the torque load on the spindle rises to a predetermined value.

Another object is to combine a torque-responsive clutch and a control spring with a motor throttle in a manner so that the control spring moves the throttle between motor starting and stop ing positions and a lockout means renders the control spring inoperative to hold the throttle open when the clutch opens.

The objects of this invention are carried out in a compressed-air-operated screwdriver by mounting a torque'opening axially moving clutch between the motor and screwdriver bit so that the clutch automatically opens when the torque load reaches a predetermined magnitude and by interconnecting a control spring means to a throttle for the motor so that the throttle opens when the tool is started during initial engagement of the screwdriver with a fastener to be driven. When the fastener is driven tight and the clutch opens under a selected torque load, the control spring means is axially moved to an inoperative position wherein the throttle can close.

The US. Pat. No. 2,964,151 issued to R. E. Eckman, discloses a power tool wherein a push-throttle rod is connected to a lock means for a torque-responsive clutch whereby the push-throttle rod collapses and closes the throttle when the clutch is opened. The present invention is to be distinguished from that patent by having the throttle rod connected to a spring which urges and holds the throttle open during the operation of the tool. The axial movement of the clutch, during its opening movement, compresses the spring thereby allowing the throttle to close. The throttle closes progressively in step with the axial movement of the clutch; hence the throt tle begins to close as the clutch begins to open; not after the clutch has opened completely.

BRIEF DESCRIPTION OF DRAWING The invention is described in connection with the accompanying drawings wherein:

FIG. I is an elevational view with parts broken away of a power screwdriver containing the invention;

FIG. 2 is a fragmentary section on an enlarged scale of the screwdriver of FIG. 1 showing the throttle valve in its open position;

FIG. 3 is a fragmentary section similar to FIG. 2 and showing the clutch in its open position with the throttle valve closed;

FIG. 4 is a fragmentary section similar to FIGS. 2 and 3 and showing the clutch in its final position with the throttle valve closed; and

FIG. 5 is a section taken on line 5-5 of FIG. 3.

DESCRIPTION OF PREFERRED EMBODIMENT The power'operated screwdriver 1 shown in the drawings includes a hollow cylindrical casing formed by a rear portion 2 and a front portion 3 threadedly connected to the rear portion 2. The rear casing portion 2 houses a conventional pneumatic motor 4 driving an output shaft 5 through a set of reduction gears 6. The output shaft 5 is mounted at its front end on a bearing 7 carried by the front end of the rear casing portion 2. The front casing portion 3 also includes a reduced-diameter nose 8 on its front end. The nose 8 contains a conventional tool holder or chuck 9 which is rotatively mounted in a journal bearing I0 in the rear end of the nose 8. The tool-holding chuck 9 contains a polygonal socket 11 adapted to receive various types of tools, fastener-engaging spindles or tips such as the screwdriver tip 12. All of the foregoing structure is conventional and usually found in power-operated screwdrivers.

The torque-release clutch mechanism of this invention provides a drive connection between the output shaft 5 and the tool-holding chuck 9. It includes a short splined drive shaft l4 which extends axially slidably into the rear part of the front casing portion 3 and is seated in a cooperating splined socket socket in the output shaft 5, thus providing an axiaI-slidable drive connection between the drive shaft 14 and the motor. The front end of the drive shaft I4 includes a rear clutch plate 15 containing a forwardly opening axial bore I6. The rear end of a clutch shaft I7 is rotatably mounted in the axial bore 16 by ball bearings 18 seated in cooperating grooves. The clutch shaft [7 is integral with the chuck 9.

A front clutch plate 22 is slidably keyed on the clutch shaft [7 in front of the rear clutch plate [5 by several key balls 23 engaging longitudinal grooves. The rear clutch plate I5 rotates on the ball bearings I8 when the clutch plates 15 and 22 are open; thus the ball bearings 18 prevent the rear clutch plate IS from sliding relative to the clutch shaft 17.

The rear and front clutch plates 15 and 22 are intercon nected together by a series of circumfe rentially interengaging cam teeth 24 formed in the adjacent faces of both clutch plates and providing a driving connection between the two clutch plates 15 and 22 so long as the plates are pressed together and the torque load carried by the clutch plates is not sufficient to disengage them. The two clutch plates I5 and 22 and the cam teeth 24 form a cam-thrust" clutch 25.

The front clutch plate 22 is biased against the rear clutch plate 15 by a heavy compression spring 28 which is engaged at its front end by an adjustment mechanism for varying the compression load on the spring 28. The compression force exerted by the heavy spring 28 tends to keep the cam teeth 24 engaged during the transmission of a torque load through the "camthrust" clutch 25. When the torque on the clutch plates 15 and 22 reaches a predetermined magnitude, determined by the load on the spring 28, the cam teeth 24 disengage and cam-thrust the front clutch plate 22 forwardly, against the spring 28, thus releasing the "cam-thrust" clutch 25. The magnitude of torque at which the cam teeth 24 disengage is changed by varying the compression load on the spring 28. The torque value at which the "cam-thrust"clutch 25 will release rises as the load on the spring 28 increases and drops as the spring load decreases. The adjustment mechanism for the spring 28 includes a nut 29 threaded on the front end of the clutch shaft 17.

A valve control sleeve 30 is slidably keyed on the clutch shaft 17 in front of the front clutch plate 22 by a crossbar 3| extending diametrically through longitudinal slots 32 formed in the clutch shaft I7. The control sleeve 30 is biased rearwardly against the front clutch plate 22 by a light spring 34 extending between the front of the control sleeve 30 and a shoulder 35 formed on the clutch shaft 17.

When the torque load transmitted by the cam-thrust" clutch 25 reaches a predetermined value or magnitude, the cam teeth 24 disengage and force both the front clutch plate 22 and the control sleeve 30 to move forwardly on the clutch shaft I7 to the forward position shown in FIG. 3. After this operation occurs, the control sleeve 30 is locked in a forward position and the front clutch plate 22 again moves rearwardly as the cam teeth 24 reengage.

The means for locking the control sleeve 30 in its forward osition shown in FIG. 4 includes a group of lock balls 37 carried in radial holes in the clutch shaft 17 and biased outwardly into an annular groove 38 formed in the interior of the control sleeve 30. The lock balls 37 are biased radially outward by a conical cam 40 carried on the rear end of the screwdriver tip I2 and sliding in the clutch shaft 17 for a limited travel.

The conical cam 40 is moved rearwardly relative to the clutch shaft l7, to bias the lock balls 37 outwardly, by the relative forward movement of the screwdriver tip I2 in the socket 11 when the screwdriver tip 12 is pressed axially against a fastener by an operator. A small spring 41 urges the screwdriver tip 12 forwardly to unlock the control sleeve 30 when the axial force against the screwdriver tip I2 is released.

During the initial engagement of the screwdriver tip 12 with a fastener, to start the screwdriver I, the cam 40 initially engages the lock balls 37 and stops moving rearward since the lock balls 37 cannot move outwardly. Later, when the clutch 25 opens and the control sleeve 30 moves forward, the lock balls 37 move outward into the annular groove 38 as shown in FIG. 3 and the conical cam 40 moves between the lock balls 37 causing them to lock the control sleeve 30 in the forward position shown in FIG. 4.

The tool is fed pneumatic fluid pressure through a supply hose attached to a fitting 45 mounted on the rear casing portion 2 of the tool. The pneumatic pressure flows from the fitting to a throttle valve 46 (shown as a ball valve) which controls the admission of the pressure to a motor supply passage 47. When the valve 46 is moved rearwardly to an open position, as shown in FIG. 2, pneumatic pressure flows past the valve 46 to the motor supply passage 47 and then to the motor 4. The flow of pneumatic pressure fluid into the passage 47 is stopped by moving the valve 46 forwardly to its seated position, as shown in FIG. 3. The fluid pressure in the fitting 45 acts as an air spring to hold the valve 46 in its closed position until such time that it is forced rearwardly to its open position.

The throttle valve 46 is opened by means of a push rod 48 which slides in an axial passage extending from the crossbar 31 through the clutch shaft l7, the drive shaft 14, the output shaft 5, the reduction gears 6 and the motor 4 to engagement with the throttle valve 46. The length of the pushrod 48 is dimensioned to allow the throttle valve 46 to close when the axial force on the screwdriver tip 12 is relaxed and to force the throttle valve 46 open when the screwdriver tip I2 is initially forced against a fastener, as shown in FIG. 2. When the opera tor presses screwdriver tip 12 against the fastener the tip I2 is pressed rearwardly against the lock balls 37 and the clutch shaft 17 is moved rearwardly until the rear clutch plate abuts the bearing 7. This is the rearward movement that opens the valve 46. When the cam-thrust clutch opens, as shown in FIG. 3, the control sleeve moves forward and allows the push rod 48 to move forward, thus releasing the throttle valve 46 whereby it canclose and stop the operation of the fluid motor 4 as shown in FIGS. 3 and 4.

OPERATION Prior to the start of operation, the screwdriver I is in the condition shown in FIG. I. The "cam-thrustclutch 25 is closed and the control sleeve 30 is unlocked. The conical cam 40 is withdrawn from the lock balls 37, the clutch shaft 17 is in its forward position, the lock balls 37 are not biased radially outward, and the push rod 48 is allowed to move forward whereby the throttle valve 46 is closed; thus the motor 4 of the screwdriver I is stopped.

Before using the screwdriver I. the nut 22 is turned until the heavy spring 28 is loaded to the desired magnitude, which determines the predetermined magnitude of torque under which the "cam-thrust" clutch 15 will open.

Initially, to tighten a fastener, the screwdriver spindle or tip 12 is placed against the head of a fastener and the screwdriver I is pressed axially forward to force the tool-holding clutch shaft 17 axially rearward in the casing 2. During the initial rearward movement of the screwdriver tip [2, once the cam 40 engages the lock balls 37 and, as a result, is prevented from moving further rearward in the bore of the clutch shaft I7, further rearward movement of the screwdriver tip 12 pushes the clutch shaft 17 rearward. The rearward movement of the clutch shaft I7 carries the control sleeve 30 and crossbar 3| rearward, resulting in pushing the push rod 48 rearward to open the throttle valve 46. The opening of the throttle valve 46 admits fluid pressure to the passage 47 and thence to the operating motor 4, which begins to drive the drive shaft 14. It will be noted that the light spring 34 must have sufficient strength to open the valve 46 without collapsing.

As the drive shaft I4 rotates, its drive torque is transmitted through the cam-thrust" clutch 25, to the screwdriver tip 12, thus driving the fastener inwardly into its hole. During this step, the parts of the clutch mechanism of the screwdriver l are arranged as shown in FIG. 2.

As the fastener is driven into place by the screwdriver l and "seated," the torque load on the cam-thrust" clutch 25 rises rapidly until it reaches a magnitude sufficient to Cause the cam teeth 24 to disengage and, as a result, to cam-thrust the front clutch plate 22 and the control sleeve 30 forward on the clutch shaft 17, compressing the spring 34, as shown in FIG. 3.

The magnitude of torque on the "cam-thrus clutch corresponds to the torque load on the fastener being tightened; hence the fastener is fully tightened when the "cam-thrust" clutch 25 opens. when the control sleeve 30 arrives at its fully retracted position, shown in FIG. 3, the lock balls 37, previously placed under an outward biasing force, move outwardly into the annular groove 38, to lock the control sleeve 30in its forward retracted position.

Thereafter, the cam teeth 24 reengage and allow the front clutch plate 22 under the biasing force of the spring 28, to return to its rearward seated position, as shown in FIG. 4.

As the control sleeve 30 and its crossbar 31 move forward, compressing the light spring 34, the push rod 48 is allowed also to move forward, as shown in FIG. 3. The forward movement of the push rod 48 closes the throttle valve 46 to shut off fluid pressure to the tool motor 4. Thus, the tool motor 4 comes to a stop. The control sleeve 30 will remain in the locked-forward position shown in FIG. 4 while the operator continues pressing the screwdriver tip 12 against the fastener while the motor 4 will stop since the throttle valve 46 is closed.

The stopping of the tool motor 4 signals the operator that the fastener is tightened properly and he removes the screwdriver I from the fastener, thus allowing the screwdriver tip I2 to move axially forward. The forward movement of the tip [2 is accompanied by a corresponding relative forward movement of the conical cam 40 away from the lock balls 37, caused by the spring 4|. Thereafter, the lock balls 37 move radially inward and the control sleeve 30 is unlocked resulting in the screwdriver I returning to the condition shown in FIG.

It will be understood that although only one embodiment of the invention is specifically described, the invention may embrace various other embodiments which are obvious from an understanding of the described embodiment and are embraced within the claims of the invention.

We claim:

I. A power-operated tool comprising:

a rotary motor;

supply means for conducting motor-driving energy to said motor;

control means having alternate positions and controlling said supply means so that in one position it prevents said energy from being supplied to said motor, and in its other position, it allows said energy to flow to said motor, said control means being normally in said one position and includin biasing means urging said control means to said one position,

a tool spindle adapted to be connected to a workpiece for applying a torque load to the workpiece and operative, when pressed against the workpiece, to move said control means to its other position; i

a torque-responsive clutch which is normally closed to interconnect said spindle to said motor, said clutch being operative, in response to a predetermined torque load on said spindle, to open wherein said motor can rotate relative to said spindle, said clutch including a clutch member that moves axially when said clutch opens; spring located between said spindle and said control means and operative, in its normal position, when said clutch is closed and said spindle is pressed against a workpiece, to transmit force from said spindle to said control means to urge and hold said control means in its other position, said clutch member being operative, when moving axially during the opening of said clutch, to cause said spring to yield to an inoperative position wherein said spring no longer holds said control means in its other position; and

lock means movable in response to the opening of said clutch to hold said spring in said inoperative position wherein said control means can return to said one position preventing said motor-driving energy from flowing to said motor.

2. The tool of claim I wherein:

said lock means is operative, in response to the withdrawal of the spindle from the workpiece, to unlock said spring and allow it to return to its normal position.

3. A fluid-operated rotary tool comprising:

a housing including a fluid-operated rotary motor;

a supply passage for conducting power fluid to said motor;

a throttle valve in said passage movable between alternate positions closing and opening said passage, said throttle valve being normally closed and including biasing means urging said throttle valve to a closed position;

a tool spindle adapted to be connected to a workpiece for applying a torque load to the workpiece and operative, when pressed against the workpiece, to move said throttle valve to its open position;

a torque-responsive clutch interconnecting said spindle to said motor, said clutch being operative, in response to a predetermined torque load on said spindle, to open and disconnect said spindle from said motor, said clutch ineluding a clutch member that moves axially when said clutch opens;

a spring located between said spindle and said throttle valve and operative in its normal position, when said clutch is closed and said spindle is pressed against the workpiece, to transmit force from said spindle to said throttle valve to hold said throttle valve open during the operation of the tool, said clutch member being operative, when moving axially during the opening of said clutch, to cause said spring to yield to an inoperative position wherein said spring no longer holds said throttle valve open; and

lock means cooperating with said clutch and movable to a position in response to the opening of said clutch wherein it locks and holds said spring in said inoperative position whereby said biasing means moves said throttle valve to its closed position preventing the power fluid from driving said motor.

4. The tool ol'claim 3 wherein:

said lock means is operative, in response to the withdrawal of said spindle from the workpiece, to unlock said spring and allow it to return it to its normal position.

5. The tool of claim 4 wherein:

said clutch member acts upon and compresses said spring in an axial direction as said clutch opens.

6. The tool ofclaim 5 wherein:

said lock means includes an intermediate member interposed betwecn said spring and said clutch member and a detent means operative to latch said intermediate member in the inoperative position of said spring.

7. The tool of claim 6 wherein: said detent means is actuated by axial force applied to the spindle as the result of the operator pressing the spindle against the workpiece.

8. The tool of claim 7 wherein:

said intermediate member is an axially sliding sleeve engaging said clutch member and movable axially with said clutch member.

9. A l'luid'operated rotary tool comprising:

a housing including a fluid-operated rotary motor;

a supply passage in said housing for conducting power fluid to said motor;

a throttle valve in said passage movable between alternate positions closing and opening said passage and including biasing means urging said throttle valve to a closed position;

throttle operator means mounted in said housing and operable by an operator for moving said throttle valve to an open position to start said motor;

a tool spindle adapted to be connected to a workpiece for applying a torque load to the workpiece;

a torque-responsive clutch interconnecting said spindle to said motor, said clutch being operative, in response to a predetermined torque load on said spindle, to progressively open and disconnect said spindle from said motor, said clutch including a clutch member that moves progressively axially as said clutch opens; and

control means operative in response to the progressive axial movement of said clutch member during the opening of said clutch, to progressively close said throttle valve in step with the axial movement of said clutch member whereby said motor is progressively stopped as said clutch progressively opens.

Ill. The tool ofclaim 9 wherein:

said control means includes spring means which normally holds said throttle valve in its open position after being moved to the open position by an operator.

11. The tool of claim 10 wherein:

said spring means is moved to its inoperative position, wherein it no longer holds said throttle valve open, by the movement of said clutch to its open position.

12. The tool of claim ll including:

lock means to hold said spring means in its inoperative position after being moved to said inoperative position by said clutch.

13. The tool of claim 12 wherein:

said throttle valve is mechanically connected to an intermediate member disposed between said spring means and said clutch member with said spring means urging said intermediate member axially against said clutch member and said clutch member moving said intermediate member axially to allow said throttle valve to close as said clutch opens.

14. The tool of claim l3 wherein:

said lock means latches said intermediate member in the closed position of said throttle valve after said clutch opens. 

1. A power-operated tool comprising: a rotary motor; supply means for conducting motor-driving energy to said motor; control means having alternate positions and controlling said supply means so that in one position it prevents said energy from being supplied to said motor, and in its other position, it allows said energy to flow to said motor, said control means being normally in said one position and including biasing means urging said control means to said one position, a tool spindle adapted to be connected to a workpiece for applying a torque load to the workpiece and operative, when pressed against the workpiece, to move said control means to its other position; a torque-responsive clutch which is normally closed to interconnect said spindle to said motor, said clutch being operative, in response to a predetermined torque load on said spindle, to open wherein said motor can rotate relative to said spindle, said clutch including a clutch member that moves axially when said clutch opens; a spring located between said spindle and said control means and operative, in its normal position, when said clutch is closed and said spindle is pressed against a workpiece, to transmit force from said spindle to said control means to urge and hold said control means in its other position, said clutch member being operative, when moving axially during the opening of said clutch, to cause said spring to yield to an inoperative position wherein said spring no longer holds said control means in its other position; and lock means movable in response to the opening of said clutch to hold said spring in said inoperative position wherein said control means can return to said one position preventing said motor-driving energy from flowing to said motor.
 2. The tool of claim 1 wherein: said lock means is operative, in response to the withdrawal of the spindle from the workpiece, to unlock said spring and allow it to return to its normal position.
 3. A fluid-operated rotary tool comprising: a housing including a fluid-operated rotary motor; a supply passage for conducting power fluid to said motor; a throttle valve in said passage movable between alternate positions closing and opening said passage, said throttle valve being normally closed and including biasing means urging said throttle valve to a closed position; a tool spindle adapted to be connected to a workpiece for applying a torque load to the workpiece and operative, when pressed against the workpiece, to move said throttle valve to its open position; a torque-responsive clutch interconnecting said spindle to said motor, said clutch being operative, in response to a predetermined torque load on said spindle, to open and disconnect said spindle from said motor, said clutch including a clutch member that moves axially when said clutch opens; a spring located between said spindle and said throttle valve and operative in its normal position, when said clutch is closed and said spindle is pressed against the workpiece, to transmit force from said spindle to said throttle valve to hold said throttle valve open during the operation of the tool, said clutch member being operative, when moving axially during the opening of said clutch, to cause said spring to yield to an inoperative position wherein said spring no longer holds said throttle valve open; and lock means cooperating with said clutch and movable to a Position in response to the opening of said clutch wherein it locks and holds said spring in said inoperative position whereby said biasing means moves said throttle valve to its closed position preventing the power fluid from driving said motor.
 4. The tool of claim 3 wherein: said lock means is operative, in response to the withdrawal of said spindle from the workpiece, to unlock said spring and allow it to return it to its normal position.
 5. The tool of claim 4 wherein: said clutch member acts upon and compresses said spring in an axial direction as said clutch opens.
 6. The tool of claim 5 wherein: said lock means includes an intermediate member interposed between said spring and said clutch member and a detent means operative to latch said intermediate member in the inoperative position of said spring.
 7. The tool of claim 6 wherein: said detent means is actuated by axial force applied to the spindle as the result of the operator pressing the spindle against the workpiece.
 8. The tool of claim 7 wherein: said intermediate member is an axially sliding sleeve engaging said clutch member and movable axially with said clutch member.
 9. A fluid-operated rotary tool comprising: a housing including a fluid-operated rotary motor; a supply passage in said housing for conducting power fluid to said motor; a throttle valve in said passage movable between alternate positions closing and opening said passage and including biasing means urging said throttle valve to a closed position; throttle operator means mounted in said housing and operable by an operator for moving said throttle valve to an open position to start said motor; a tool spindle adapted to be connected to a workpiece for applying a torque load to the workpiece; a torque-responsive clutch interconnecting said spindle to said motor, said clutch being operative, in response to a predetermined torque load on said spindle, to progressively open and disconnect said spindle from said motor, said clutch including a clutch member that moves progressively axially as said clutch opens; and control means operative in response to the progressive axial movement of said clutch member during the opening of said clutch, to progressively close said throttle valve in step with the axial movement of said clutch member whereby said motor is progressively stopped as said clutch progressively opens.
 10. The tool of claim 9 wherein: said control means includes spring means which normally holds said throttle valve in its open position after being moved to the open position by an operator.
 11. The tool of claim 10 wherein: said spring means is moved to its inoperative position, wherein it no longer holds said throttle valve open, by the movement of said clutch to its open position.
 12. The tool of claim 11 including: lock means to hold said spring means in its inoperative position after being moved to said inoperative position by said clutch.
 13. The tool of claim 12 wherein: said throttle valve is mechanically connected to an intermediate member disposed between said spring means and said clutch member with said spring means urging said intermediate member axially against said clutch member and said clutch member moving said intermediate member axially to allow said throttle valve to close as said clutch opens.
 14. The tool of claim 13 wherein: said lock means latches said intermediate member in the closed position of said throttle valve after said clutch opens. 